© 2004 Plano ISD, Plano, TX What is a model?

© 2004 Plano ISD, Plano, TX A scientific model is a smaller or larger representation (pattern, plan, replica, or description) designed to show the structure/function of the real thing is a smaller or larger representation (pattern, plan, replica, or description) designed to show the structure/function of the real thing usually contains the smallest number of parts that are necessary to describe the real thing usually contains the smallest number of parts that are necessary to describe the real thing can be static or dynamic is a simplification can represent an object, system, or concept

© 2004 Plano ISD, Plano, TX A scale model can use the same or different materials as the original but the dimensions must be proportionate. Examples: maps blueprints architectural drawings Examples: maps blueprints architectural drawings can be a working model (cockpit simulator) scale given in key/legend (ex. 1” = 1 mi)

© 2004 Plano ISD, Plano, TX A simulation model simulates the behavior of something. used in computer games, programs involves input from the user (joystick, mouse, throttle, remote control, keyboard), and output involves input from the user (joystick, mouse, throttle, remote control, keyboard), and output uses mathematical functions

© 2004 Plano ISD, Plano, TX Examples of Scientific Models

© 2004 Plano ISD, Plano, TX Because atoms and molecules are so small, several types of models are used to represent molecular structure in chemistry. perspective drawing - 2D geometric model of atoms and bonds perspective drawing - 2D geometric model of atoms and bonds ball and stick - 3D model of atoms and bonds ball and stick - 3D model of atoms and bonds H HÖ: HH O : : space filling - 3D model of atoms and bonds space filling - 3D model of atoms and bonds -or-

© 2004 Plano ISD, Plano, TX Models of the Universe Scientists have always searched for an explanation of how the universe was formed Over the years many theories have developed The balloon model represents what we presently know about the universe. The Universe (balloon) is getting larger, and the galaxies (dots) are moving apart from each other.

© 2004 Plano ISD, Plano, TX Steady State Theory galaxies are not moving away from each other new stars are being made from energy in the center of the galaxies But if the balloon model it right, does Steady State make sense????

© 2004 Plano ISD, Plano, TX Big Bang Theory Proposed by Georges Lemaitre 1926 Galaxies are expanding in all directions Must have started at a central location with an explosion Does the balloon model work for this theory??

© 2004 Plano ISD, Plano, TX Oscillating-Universe Theory universe has gone through periods of expansion and contraction the universe is currently in a period of expansion What would have to happen to the balloon for this theory to work?

© 2004 Plano ISD, Plano, TX Expansion Theory universe is expanding faster than it did a few million years ago 1% growth every 200 million years

© 2004 Plano ISD, Plano, TX Limitations of Models

© 2004 Plano ISD, Plano, TX Because a model is a simplification, it is necessary to realize that the final result may not give a completely true description of the object or system. What are the limitations of these models?